So if InfiniBand is designed to address the shortcomings of PCI, is it also designed to replace PCI? While initially some felt InfiniBand could result in the demise of PCI, it is actually designed to solve needs different than those addressed by PCI.

InfiniBand focuses on server technology I/O issues, not those of the personal computer. The InfiniBand fabric is also not designed to support consumer installations of expansion cards, another point that relegates it to the server realm rather than making it ideal for consumer deployment.

Before wrapping up our discussion of InfiniBand, let’s review three primary components involved in making up the InfiniBand fabric. These are:

Host Channel Adapter (HCA): The HCA is the interface that resides directly inside the server and provides the communication between the processor, the InfiniBand fabric, and the server’s memory. The HCA can be added to a server using the PCI slot, or it can be integrated onto the system board.

Target Channel Adapter (TCA): The TCA adapter allows I/O devices such as tape storage to be part of the fabric independent of a host computer. The TCA uses an I/O controller to specify the network protocol used (Ethernet, Fibre Channel, or SCSI).

Switch: The switch is the connection point for the HCAs and TCAs. The switch regulates traffic by looking at the route header and forwarding the data to the correct location. A connected group of switches is referred to as the fabric.

Fabric Shortest Path First (FSPF)

Moving away from InfiniBand but staying within the realm of fabrics, we have the Fabric Shortest Path First (FSPF) protocol. A storage network uses redundant interlink switches to create a fully meshed fabric. This fabric is essential for ensuring high availability, high performance, and load balancing.

When data is transmitted over a fabric network there are redundant paths or routes it can travel. The FSPF protocol provides a common mechanism to allow for efficient route selection. In other words, FSPF identifies the best path between two switches in the fabric and then updates routing tables to use that path.

Those who have worked with IP networks will no doubt notice a name similarity between Fibre Shortest Path First and the Open Shortest Path First (OSPF) routing protocol used on Ethernet networks. FSPF is indeed a derivative of its IP cousin, and both are link state protocols.

FSPF is part of the Fibre Channel Protocol (FCP). A properly designed fabric requires a knowledge of FSPF in order to minimize bottlenecks, supply adequate bandwidth, and minimize connection costs.